Treatment of lead minerals



Patented Aug. 4, 1925.

V UNITED STATE FF! ca.

LOUIS r. CLARK, or JERSEY our, NEW Jnnsnv.

TREATMENT or LEAD MINERALS.

No Drawing.

Treatment of Lead Minerals, of which the following is a specification.

My invention aims to provide a process I by which lead minerals can bemade susceptible to concentration by the flotation method.v Not allvaluable minerals are amenable to flotation concentration. Generallyonly such as are called sulphides respond to such treatment. The otherminerals, or such as may be called oxides because oxygen rather thansulphur is an important part of their composition, must first be given apreliminary treatment to make them recoverable in a flotationconcentrate.

Minerals of lead are especially apt to fall under the aboveclassification of sulphides and oxides. The sulphides will float and theoxides not. T have found, however, that when the oxides are given apreliminary coating of anorganic substance, they too become flotable. lThe following description will show how such a substance of organicnature may be applied to the particles of lead mineral. Theoperationsare performed in a pulp, that is, a mixture of finely groundore and water. In such acondition the lead minerals may be considered asindividual small particles whose surfaces may be modified by othersubstances dissolved in the water of the pulp. These reactions may beeffected in various Ways, as follows:

(a) Treatment of a pulp containing an oxide of lead, for example, leadcarbonate, with an alkali bichromate, for example,

'Na Cr O in a neutral or slightly acid solution to form a coating oflead chromate. This may advantageously be done in a solution'havingcopper sulphate dissolved together with the alkali bichromate, or by asolution of copper bichromate itself. The equation for this last willindicate the net result of any such combination,

'on the surface of the lead minerals are relsubstances except in ativelyinsoluble This operation stronger acid solutions.

Application filed April 23, 1924. Serial No. 708,330.

should be conducted with small and insufficlent amounts of the dissolvedsalts present -to react with the total weight of lead carbonate in theportion of ore treated so as to merely coat the lead; minerals andalmclist completely consume the dissolved sa ts.

After the above coating has been formed the lead minerals have a surfacewhich is capable of oxidizing and so precipitating many organicsubstances which may now be introduced into the solution. A particularlyimportant reagent far this purpose is aniline oil or an acid salt ofaniline. This may so be dissolved in the water of the pulp and a finalcoating of the organic oxidation product known as aniline black formedon the surface of the lead minerals. Other substances may serve the samepurpose, for example, linseed oil, turpentine, pine oil, etc.

The function of the cop-per salt mentioned together with the alkalibichromate is to catalyze the final oxidation reaction between thechromate and the organic substance, for example, aniline, dissolved.There 'may, however, be sufficient copper mineral naturally associatedwith the lead carbonate so that its use in the operation may be omitted.On the other hand, the use of the copper salt in the operation may bedelayed until the aniline is also dissolved. In this case a coating oflead chromate only would be formed. This would then be modified by asolution of say aniline and copper sulphate dissolved together to formthe final organic resin coating on the lead minerals.

The above describes reactions which take place best in neutral or slihtly acid solutions. The following proce ure in alkaline solution may bemore desirable with some ores, for example where lead carbonate ocourswith limestone.

(b) Treatment-of a pulp with bleaching lime, calcium hypochlorite,dissolved in the water of the pulp together with aniline oil. In thiscase in alkaline solution the lead minerals act catalytically at theirsurface to complete the oxidation of the aniline froni the blue solutionformed when it isdissolved with calcium hypochlorite, probably byincipient precipitation of lead dioxide. The net result is however theformation of the insoluble organic resin coating on the surface of thelead minerals. Other oxidizing agents in alkaline solution may besimimay be adopted for some ores. This may consists in applying apreliminary coating of a copper compound on the surface of the leadminerals in neutral or alkaline solution as previously mentioned.Equations illustrating these conditions follow rboo, CuSO, PbSO 01100..

This is a reciprocal precipitation from a solution of copper sulphate bythe solid grains of lead carbonate to form the two a new and relativelyinsolublesubstances, lead sulphate and copper carbonate.

' attained by other salts of copper dissolved.

After this preliminary coating with a copper compound has beenaccomplished, then the procedure given in my. application No. 671,392may be applied and in substantially the manner as therein set forth forthe treat-- ment of naturally occurring oxidized copper lead mineralsWlllCh consists in coating the minerals. This procedure consists in;applying to a pulp of the treated ore acetylene and other oxldizableorganic substances, which facilitate the reduction of the cupricminerals, so as to apply to the particles thereof a coating whichfacilitates their subsequent flotation.

The above describes methods .whereby precipitates may be first formed onthe surface of the oxide minerals of lead, such precipitates being inturn capable of oxidizing and so precipitating certain or anicsubstances which may be now broug t in contact with the modified leadminerals by being dissolved in the liquid of the pulp.

Though I have described with, great particularity of detail certainembodnnents of my invention, yet'it is not to be understood therefromthat the invention is restricted to the particular embodimentsdisclosed. Various modifications may be made in the particular steps)and in the order thereof and in the substitution of equivalent materialsby those skilled in-the art without departing from the invention asdefined in p the following claims. What I claim is:

'11. The method of treating ores containing lead minerals whichco'nsistsin forming on the particles of such minerals a superficial filmof lead chromate and treating the same with an organic substance tooxidize the latter and precipitate the oxidation prodnets on theparticles.

2. The process of claim 1 in which the superficial film. contains coppercarbonate as .well as lead chromate.

3. The method of treating ores containing lead minerals which-consistsin subjecting the particles to the action of lead chromate and coppersulphate in a solution of an organic.substance'adapted to be oxidized sothat the oxidation products are precipitated on the particles.

4. The method of treating ores containing particles preliminarily with acopper compound and then applying a coating containing cuprous acetyide.

Inwitness whereof, I have' hereunto signed my name.

LOUIS F." CLARK.

